Honeycomb panels are frequently used in the aircraft industry and in other industrial applications. By "honeycomb panel" is meant a panel formed of a relatively thin inner and outer skin secured to a core. While a honeycomb panel is the usual and typical application of the present invention, the invention is not limited to a panel in which the core is of honeycomb configuration but is applicable to any panel having a first and a second skin bonded to a core which may be more generally called a "sandwich panel". The purpose of the invention is to provide means for structurally reinforcing any such panel, that is, any panel having a first and second skin separated by a core.
A specific example of the application of this invention is for reinforcing honeycomb panels utilized on aircraft, such as in structures attached to an aircraft jet engine to reduce engine noise. Because of the high forces, drastic temperature differentials and vibration, the skin of honeycomb panels can become separated from the core or the core itself may destruct. To repair a honeycomb panel in this environment the present procedure is to use rods that are welded to join to the two skins together to thereby entrap the core. This procedure works successfully but is time consuming, particularly due to the high degree of cleanliness which must be established before effective welding can be accomplished. The tail pipe environment in which these panels are used exposes them to oil, soot, and other materials. Cleaning the panels to put them in condition to receive effective and permanent welds is difficult. The invention herein provides a method of reinforcing honeycomb panels in which it is not necessary to thoroughly clean the panels as is required with welding procedures.
The invention herein provides a mechanical system for reinforcing skins bonded to opposed sides of a core material, such as a honeycomb core material. Specifically, the invention herein provides a method and apparatus for installing a bolt in a sandwich panel in a way to resist delamination of the skins from the core.
For background information relating to structures utilized to reinforce sandwich panels having first and second skins with a core therebetween, reference should be had to the following United States Patents:
______________________________________ U.S. Pat. No. INVENTOR TITLE ______________________________________ 3076668 Famely Fittings For Retaining Cylindrical Members In Place 3468091 Gerhard Wall Fasteners 3526072 Campbell Load Distributing System For Panels Incorporating Honeycomb Core 4048898 Salter Fastener For Multi Metal Stack-Ups 4089247 Dahl et al Blind Fastener 4499647 Sakamura et al Blind Nut Fastening Method 4656806 Leibhard et al Expansion Anchor Assembly 4717612 Shakelford Fasteners For Honeycomb Structures 4934861 Weeks et al Attachment Apparatus For External Stores On Thin-Wall Poles 5040917 Camuffo Device For Fixing Mechanical Parts To The Body Of A Motor Vehicle 5205689 Fischer Expansible Plug ______________________________________